This invention is concerned with a floatable apparatus which includes at least two jaws or grippers useful as a clam-shell bucket or the like. The present invention concerns, more particularly, improvements to clam-shell diggers of the type constituted by at least two jaws articulated around a common axis of a lifting element. The jaws are arranged in such a way that while closed, they constitute a gripper, a pocket or a transport bucket for the materials which are clamped or contained therein. In an open position and when they are situated at the level of the body or bodies to be grasped or when they lie on the bottom of a water basin, they constitute two grasping elements or two digging elements. The removal or excavation is effected by a simple approachment of the jaws toward one another, upon an appropriate command. The closure and approachment of the jaws are, in fact, effected by conventional devices, either by use of appropriate cables or by action of hydraulic jacks. In all cases, these prior art techniques and devices are incapable of permitting the removal of very large quantities of soil, of the order for example of several hundreds of tons, in one single operation at some considerable depth of water, such as for example at sea bottom. With conventional techniques it would be necessary:
EITHER TO ARRANGE ABOVE THE REMOVAL AREA FOR A FLOATING PONTOON WHICH CARRIES THE MANEUVERING APPARATUS OF THE CLAM-SHELL DIGGER AND GENERALLY CONSTITUTED BY A CRANE, AND SUBSEQUENTLY BY MANEUVERS OF DESCENT, GRASPING AND LIFTING IN SUCCESSION, TO DISCHARGE THE REMOVED SOIL INTO A NEARBY VESSEL, WHICH, ONCE FILLED UP, MUST RETURN TO THE DISCHARGE AREA WHILE IT IS POSSIBLY REPLACED BY ANOTHER IDENTICAL VESSEL IN THE VICINITY OF THE CRANE; THE RISKS CONNECTED WITH SUCH MANEUVERS, ESPECIALLY DURING HEAVY SEAS, ARE WELL KNOWN;
OR, IT IS NECESSARY TO EMPLOY AN EXCAVATION APPARATUS, SUCH AS IS DEFINED ABOVE, AND WHICH ITSELF CONSTITUTES A PART OF A VESSEL, BUT THEN THERE RESULTS A VERY POOR UTILIZATION OF THE EQUIPMENT, BECAUSE DURING THE PERIODS OF COMING AND GOING BETWEEN THE DISCHARGE PORT AND THE AREA OF REMOVAL, CONSIDERABLE PORTIONS OF THE EQUIPMENT ARE UNUSED FOR SIGNIFICANT PERIODS.
It is known, incidentally, to make vessels whose hulls are constituted of two symmetrical halves with respect to the median plane, and which are articulated toward each other around an axis, in a general form of jaws and where each of these halves is equipped with floatation chambers or caissons into which water may be admitted or from which it may be purged by the action of compressed air. However, in such vessels the opening and closing of the jaws is effected by an independent device, such as hydraulic jacks, which mechanically act upon the jaws in the sense of effecting their opening or their closing. This presents numerous inconveniences, especially whenever one intends the utilization of the apparatus at great depths.